The surfaces of many cells are covered with a transparent coat of hyaluronate (HA). It appears that the HA is retained at the cell surface through a covalent linkage to a small core protein. The cell coat has been shown to act as a physical barrier, protecting cultured cells from: (1)\virus infection, (2)\the cytotoxic effector cells of the immune system, and (3)\agglutination by lectins. The surfaces of cultured cells also have binding sites for HA. Virus transformation of cultured cells results in a significant reduction in the size of the HA-containing cell coat. Earlier results indicated that virus-transformation causes an increase in the number of HA binding sites which are available on the cell surface. There appears to be an inverse relationship between the size of the HA cell coat and the number of HA binding sites available on the cell surface. Our objectives are to examine the structure and function of the HA cell coat and binding sites for HA with respect to the characteristics of virus-transformed cells. The specific aims are divided into three major areas: (1)\To determine if the number of HA binding sites changes after virus transformation. The apparent increase in the number of HA binding sites following virus-transformation could be due to the loss of cell surface HA. The number of HA binding sites on parent and virus-transformed cells will be measured using two different techniques; (a)\measuring the binding of 3H-HA to binding sites which have been solubilized with a detergent, and (b)\directly quantitating the amount of a 85,000 Mr protein which has been tentatively identified as the binding site. The results of this study should indicate whether the amount of the binding site can be used as a marker for virus-transformed cells. (2)\To determine if differences in the sizes of the HA coats of parent and virus-transformed cells can account for some of the differences observed between these cells with respect to: (a)\lectin mediated agglutination, and (b)\cell-mediated cytotoxicity reactions. Parent and virus-transformed cells will be tested both before and after removal of the cell coat with HAase. (3)\To examine the structure of the core protein, which is covalently attached to the HA, the following will be undertaken: (a)\the bond between the core protein and the HA will be identified, (b)\the sugars present in the linkage region will be analyzed, and (c)\the precursor form of the core protein will be isolated using an immunological approach. (AG)